Implement the Radial Histogram Equalizing Filter

[GillySpace27]

Describe the feature

I would like to contribute one of the results of my thesis work (found at https://www.proquest.com/docview/2759080511) called the Radial Histogram Equalizing Filter. It is a hybrid adaptive histogram equalizing filter and radial graded filter, and would live in the Radial module or the Enhancement module.

Proposed solution

I have already forked the repo and implemented the algorithm and a test for it, but now it just needs more tests and probably some stylistic changes.